Distractions and the risk of car crash injury: the effect of drivers' age

PROBLEM: Motor-vehicle accidents are one of the major causes of injury in most motorized countries. Driver distractions have been suggested as a contributor to traffic accidents. Moreover, age of the driver seems to have a role in the relationship between distractions and car crashes. But very few studies have investigated the effect of driver's age on this relationship. This exploratory study investigated the association between distractions, both inside and outside the vehicle, and the increased risk of car crash injury among drivers across different ages. METHOD: This study used a case series design to analyze data routinely collected by the NSW police in Australia. A special focus of this study was on how drivers' age affects the risk of car crash injury, which was determined by using a well-documented risk estimation methodology. RESULTS: The results obtained indicated that drivers of all ages, on the whole, are more susceptible to distractions inside the vehicle than distractions coming from outside. Age was shown to affect the relationship between in-vehicle distraction and the risk of car crash injury. A separate analysis was also conducted on hand-held phone usage while driving with results supplementing previous findings reported in the literature. IMPACT TO INDUSTRY: Safety strategies to countermeasure in-vehicle distractions have been suggested and discussed.     

Transport and degradation of toluene and o-xylene in an unsaturated soil with dipping sedimentary layers

A lysimeter trench was established at the Gardermoen delta (50 km north of Oslo, Norway) to study the flow of water and transport and degradation of aromatic jet fuel components (toluene and o-xylene) in the undisturbed unsaturated zone. Site investigations with ground-penetrating radar revealed the presence of dipping sedimentary layers within the foreset unit. This study has shown that the foreset bed of the Gardermoen delta structure provided a preferential flow path for the transport of the solute plumes, but did not have dramatic effects on the degradation potential under the current conditions. The degradation potential for toluene and o-xylene in the unsaturated zone at Gardermoen was very high and almost all of the injected hydrocarbons were biodegraded before reaching the saturated zone. However, the horizontal displacement of the plume showed that knowledge about sedimentary structures in the unsaturated zone is important for a sufficient monitoring of contaminant transport and for remediation purposes. Carbon dioxide and O2 were measured in situ simultaneously with extraction of water samples, and indicated aerobic biodegradation of toluene and o-xylene. Overall, first-order degradation coefficients were calculated to be in the range of 0.19 to 0.21 d(-1) and 0.10 to 0.11 d(-1) for toluene and o-xylene, respectively.     

Rhizosphere acidification and cadmium uptake by strawberry clover

Strawberry clover (Trifolium fragiferum L.) is a hardy legume found in indigenous or introduced populations throughout the world. Tolerance to saline and alkaline soils, flooding, and heavy metals make it a good prospect for reclamation projects. The research, described here, was conducted to: (i) characterize the morphological variation in plants from available seed sources, (ii) evaluate cadmium uptake and tolerances over a wide range of morphological variants, and (iii) elucidate the variability in the effects of roots on rhizosphere pH and the relationship to cadmium uptake. Seeds from selected accessions were planted in the greenhouse for comparison of morphological variation. The accessions examined had a mean height of 10.7+/-7 cm. Accessions 254916 and 237925 are tall with high rhizosphere pH values and might be useful in phytoremediation. Strawberry clover accessions were also grown hydroponically to examine differences in cadmium uptake. The ability of strawberry clover roots to change rhizosphere pH and take up cadmium was examined using culture tubes containing nutrient agar, a moderate level of cadmium, and a pH indicator dye. The results provided evidence for a negative correlation between rhizosphere pH and cadmium uptake.     

Real-time, high-resolution quantitative measurement of multiple soil gas emissions: selected ion flow tube mass spectrometry

A new technique is presented for the rapid, high-resolution identification and quantification of multiple trace gases above soils, at concentrations down to 0.01 microL L(-1) (10 ppb). The technique, selected ion flow tube mass spectrometry (SIFT-MS), utilizes chemical ionization reagent ions that react with trace gases but not with the major air components (N2, O2, Ar, CO2). This allows the real-time measurement of multiple trace gases without the need for preconcentration, trapping, or chromatographic separation. The technique is demonstrated by monitoring the emission of ammonia and nitric oxide, and the search for volatile organics, above containerized soil samples treated with synthetic cattle urine. In this model system, NH3 emissions peaked after 24 h at 2000 nmol m(-2) s(-1) and integrated to approximately 7% of the urea N applied, while NO emissions peaked about 25 d after urine addition at approximately 140 nmol m(-2) s(-1) and integrated to approximately 10% of the applied urea N. The monitoring of organics along with NH3 and NO was demonstrated in soils treated with synthetic urine, pyridine, and dimethylamine. No emission of volatile nitrogen organics from the urine treatments was observed at levels >0.01% of the applied nitrogen. The SIFT method allows the simultaneous in situ measurement of multiple gas components with a high spatial resolution of < 10 cm and time resolution <20 s. These capabilities allow, for example, identification of emission hotspots, and measurement of localized and rapid variations above agricultural and contaminated soils, as well as integrated emissions over longer periods.     

Relationships between bacterial tolerance levels and forms of copper and zinc in soils

The effects of various fractions of copper (Cu) and zinc (Zn) on soil bacteria were evaluated by the heavy metal tolerance level of the bacterial community (IC50) in soil samples collected near a mine. The IC50 values had no relationship with the total concentrations of Zn and Cu in the soils, but were weakly correlated with the 0.05 M CaCl2-extractable form of each metal in the soils (Cu: R2 = 0.670, p < 0.01; Zn: R2 = 0.453, p < 0.05). It was found that the IC50 correlated strongly with the total concentration of each metal in the extracts from water-saturated soil samples, described below as "soil solution" (Cu: R2 = 0.789, p < 0.01; Zn: R2 = 0.617, p < 0.01). The speciation of these metals in the soil solutions was estimated using an equilibrium thermodynamic computer model, SOILCHEM. Simulated free Cu ion ranged from 18 to 98% of total Cu, and organic complexes of Cu ranged from < 1 to 56%. In all samples, Zn existing as the free ion was estimated to be more than 80% of total Zn in the soil solutions. The IC50 values were also correlated with the estimated free metal ion activities, but with slightly lower correlation coefficients than found for total concentration in the soil solutions (Cu: R2 = 0.735, p < 0.01; Zn: R2 = 0.610, p < 0.01). The results suggest that not only high metal ion activities, but also total dissolved metal concentrations in soil solutions may affect the bacterial community.     

Vegetation stress detection through chlorophyll a + b estimation and fluorescence effects on hyperspectral imagery

Physical principles applied to remote sensing data are key to successfully quantifying vegetation physiological condition from the study of the light interaction with the canopy under observation. We used the fluorescence-reflectance-transmittance (FRT) and PROSPECT leaf models to simulate reflectance as a function of leaf biochemical and fluorescence variables. A series of laboratory measurements of spectral reflectance at leaf and canopy levels and a modeling study were conducted, demonstrating that effects of chlorophyll fluorescence (CF) can be detected by remote sensing. The coupled FRT and PROSPECT model enabled CF and chlorophyll a + b (Ca + b) content to be estimated by inversion. Laboratory measurements of leaf reflectance (r) and transmittance (t) from leaves with constant Ca + b allowed the study of CF effects on specific fluorescence-sensitive indices calculated in the Photosystem I (PS-I) and Photosystem II (PS-II) optical region, such as the curvature index [CUR; (R675.R690)/R2(683)]. Dark-adapted and steady-state fluorescence measurements, such as the ratio of variable to maximal fluorescence (Fv/Fm), steady state maximal fluorescence (F'm), steady state fluorescence (Ft), and the effective quantum yield (delta F/F'm) are accurately estimated by inverting the FRT-PROSPECT model. A double peak in the derivative reflectance (DR) was related to increased CF and Ca + b concentration. These results were consistent with imagery collected with a compact airborne spectrographic imager (CASI) sensor from sites of sugar maple (Acer saccharum Marshall) of high and low stress conditions, showing a double peak on canopy derivative reflectance in the red-edge spectral region. We developed a derivative chlorophyll index (DCI; calculated as D705/D722), a function of the combined effects of CF and Ca + b content, and used it to detect vegetation stress.     

The influence of nitrogen deposition,competition and desiccation on growth and regeneration of Racomitrium lanuginosum (Hedw.) brid

Racomitrium lanuginosum shoot growth was studied under the combined effects of N deposition (0, 20, 40 and 60 kg N ha(-1) year(-1)). competition with Festuca ovina, and a drought pre-treatment. Moss regeneration from shoot fragments was also investigated. Growth was initially stimulated at the 60 kg N level. However, after 6 months, growth was lower in all N treatments than in the 0 kg N control. Reductions in shoot growth first became apparent in the pre-desiccated moss, while moss shoots grew longer when surrounded by a F. ovina canopy. Optimum regeneration occurred at 20-40 kg N on bare soil, and at 0-20 kg N under a F. ovina canopy. These results suggest that current N deposition in upland Wales is already detrimental to growth of this species, and to regeneration under certain conditions. This species may be affected under predicted climatic scenarios of increased summer drought in Britain.     

Modelling the long-term dynamics of radiocaesium in closed lakes

During the years after the Chernobyl accident the radioceasium activity concentration in most contaminated aquatic ecosystems decreased markedly. Lakes with no permanent inflows and outflows (closed lakes), however, still present a radioecological problem which is expected to continue for some time. In this paper, a mechanistic model for the long-term prediction of radiocaesium behaviour in closed lakes is developed. The model of Prokhorov (Radiokhimiya (Radiochemistry) 11 (1969) 317) was modified to describe the effects of bottom sediment bioturbation, surface runoff from the catchment and suspended solids formation and sedimentation. The model input parameters are the effective diffusion coefficient in bottom sediments, depth of the completely mixed layer, the distribution coefficient in the sediment-water system, the runoff coefficient, sedimentation rate, and deposition density. Values of all these parameters can be independently estimated or measured in a short-term experiment. Given negligible runoff and sedimentation, the dynamics of radiocaesium in lake water is described by a simple equation with only one unknown parameter. This allows us to make long-term predictions on the basis of a series of measurements carried out during the relatively short period. The model was tested against 137Cs activity concentrations measured between 1993 and 1999 in Svyatoe lake in the Bryansk region of Russia. Calculated and measured activity concentrations are in good agreement.     

An analysis of the environmental mobility of radiostrontium from weapons testing and Chernobyl in Finnish river catchments

The mobility of radiostrontium within the Arctic environment and surrounding area has been studied by analysing the mobility of 90Sr in river catchments that are within Finland. The environmental mobility of 90Sr deposited by both nuclear weapons testing and the Chernobyl accident has been investigated in five Finnish river catchments. Different models assessing the time-dependent mobility of 90Sr have been evaluated. No significant differences were found between the mobility of 90Sr from nuclear weapons tests and from the Chernobyl accident. Model parameters obtained by fitting to the measurements of the deposition and runoff rates of the nuclear weapons test fallout gave predictions which were consistent with the mid- and long-term contamination by the Chernobyl fallout. A comparison of 90Sr with 137Cs showed that they had similar mobility on deposition but, as time passed, the relative mobility of 90Sr increased with respect to 137Cs over a period of 5-8 years. Once the relative migration of 90Sr with respect to 137Cs reached equilibrium, its runoff rate was, on average, approximately an order of magnitude greater than 137Cs.     

Variability in background levels of surface soil radionuclides in the vicinity of the US DOE waste isolation pilot plant

Concentrations of radionuclides were measured in soils from a grid of locations surrounding the US Department of Energy Waste Isolation Pilot Plant (WIPP) in southeastern New Mexico and from a grid on a reference site approximately 20 km southeast of the WIPP site. Each of the two grids has 16 sampling locations (grid nodes) systematically distributed within an area of 16.580 ha. Sampling was conducted prior to the arrival of the first waste shipment at WIPP. Thus, the 137Cs and 23,240Pu in the soil are expected to have been deposited as global fallout, although the Gnome Site, 8.8 km southwest of the WIPP, is also a potential source of 239,240Pu and fission products. The reference grid has significantly higher concentrations of fallout and natural radionuclides than the WIPP grid. Up to 80% of the total variability in radionuclide concentrations across the two grids is attributable to differences between grid nodes. Differences between replicates within a location account for 44-50% of the variability in concentrations of the uranium isotopes, but only 11-17% of the variability in the concentrations of the other radionuclides. Samples having similar abundance of radionuclides were spatially aggregated across the terrain. The activity concentrations of the radionuclides were strongly correlated with the concentrations of Al and Pb, and with the percentages of sand, silt and clay in the soil. Normalizing radionuclide concentrations to the concentration of Al or percent fine particles can help adjust for differences in soil textures among samples and facilitate the detection of gradients or temporal changes in soil concentrations.